1. Field of the Invention
The present invention relates to a light intercepting apparatus which prevents harmful light from entering a lens barrel through an annular gap between a lens barrel, which moves in an optical axis direction, and a lens holding cylinder, which supports the lens barrel so as to move in the optical axis direction.
2. Description of the Related Art
In a conventional lens shutter type of compact camera having a range finder, a focal length of a photographing lens is usually not variable. However, recently, range finder type compact cameras having an autofocus function and a photographic zoom lens have been developed. In this compact camera zoom, a lens barrel advanced from the camera body during a zooming operation moves in the optical axis direction.
To smoothly advance the lens barrel from the camera body, a slight gap must be provided between the outer periphery of the lens barrel and a lens holding member which is provided on the camera body to movably support the lens barrel. Accordingly, there is a possibility that light enters the camera body through the gap between the outer periphery of the lens barrel and the lens holding member, resulting in the undesired exposure of a film in a film chamber. To prevent such an undesirable exposure by harmful light, a light intercepting apparatus, as shown in FIGS. 5 and 6 is usually provided.
In FIG. 5, a lens holding member (cylinder) 2 has a center bore 2A in which lens barrel 1 is movably inserted and which has an inner diameter having a predetermined tolerance with respect to the outer diameter of the lens barrel 1. A flock paper 4, having a predetermined width, is adhered to the inner periphery 2B at a front end of the center bore 2A of the lens holding cylinder 2, so that the inner surface of the flock paper 4 comes into sliding contact with the outer periphery of the lens barrel 1 to intercept harmful light which would otherwise enter the camera between the gap between the inner peripheral surface of the lens holding cylinder 2 and the outer peripheral surface of the lens barrel 1.
In an arrangement illustrated in FIG. 6, the annular light intercepting tongue 5, which is made of an elastic material, such as rubber or resin film or the like, is provided on front end 2C of the lens holding member 2, in addition to the flock paper 4 shown in FIG. 5. The light intercepting tongue 5 has an inner diameter which is slightly smaller than the outer diameter of the lens barrel 1. The annular light intercepting tongue 5 is deformed to increase the inner diameter thereof when the lens barrel 1 is fitted in the annular light intercepting tongue 5, so that the inner peripheral surface of the annular light intercepting tongue 5 comes into close contact at the front end thereof with the outer peripheral surface of the lens barrel 1 to intercept harmful light. The direction of front end of the annular light intercepting tongue 5 is reversible in accordance with the axial movement of the lens barrel 1 in the opposite directions. Numerals 3 and 21 in FIGS. 5 and 6 designate an outer shell and a cam ring, respectively, which actuates the lens barrel 1 to advance while rotating.
In the above mentioned conventional structures, however, the flock paper 4 hardly deforms in the direction of thickness thereof, and accordingly, a possible dimensional error or a displacement in the direction of thickness can not be effectively absorbed. Namely, possible "out of roundness" and "out of concentricity" of the lens barrel 1 and the center bore 2A of the lens holding member 2 can not be effectively absorbed by the flock paper 4. As a result, a slight gap, which causes the harmful light to enter from outside of the lens barrel 1, may exist between the lens barrel 1 and the lens holding member 2.
Furthermore, in an arrangement shown in FIG. 6 in which the light intercepting tongue 5 is additionally provided, a set screw 7 is usually used to secure some member to the lens barrel 1. The lens barrel 1 has a recess 1A in which head 7A of the set screw 7 is received. In this case, there is a possibility that harmful light enters through the recess 1A, as shown by an arrow 1 in FIG. 6.